After single mother Tereon Grant is stabbed to death in the middle of the night, all signs point to her ex-boyfriend being the killer; then, Detectives Quinn and Velazquez dig deeper into the case, uncovering a dark secret that changes everything.

When the skull of 11-year-old Alan Watson is found in a field, Quinn and Velazquez take the case of a murder that took place almost a decade before.

To trained eyes, it appears as though Shaquilla Weatherspoon's killers staged the crime scene to make it look like a robbery; knowing better, Detectives Quinn and Velazquez investigate those closest to Shaquilla to find the truth.

When U.S. Air Force veteran John Ray is found beaten and stabbed to death in his apartment, the crime scene looks like a random robbery.

New mother Sparkle Rai, 21, is found strangled to death by her boyfriend who instantly becomes the prime suspect; David Quinn and Vince Velazquez uncover a surprising new suspect from Rai's past.

Quinn and Velazquez are called when Jerry Heard is found dead from gunshot wounds. They learn Heard spends his nights at a local bar, and the night he was killed, he was flirting with two different women, one with an armed boyfriend. With at least three potential suspects, the detectives get to work.

Neighborhood character Willie Bell is found naked and dead early in the morning; with nothing else to go on, Quinn and Velazquez discover that Willie was seen with two different women the night before he was found.

Cassandra Bryant, 38, is found naked and barely clinging to life; she dies in the ambulance before identifying her attacker, leaving Quinn and Velazquez to find her killer.

When Detectives Quinn and Vince investigate the shooting of Antwan Curry, they find a trail of blood leading away from the murder scene; they set out to find the injured person, not knowing if they're looking for another victim or the killer.

Longtime partners Quinn and Velazquez are chosen to solve the case of Apriel Allen, a woman who was murdered in her apartment two years prior; the detectives begin with a clean slate and hope to bring some peace to Allen's loved ones.

After immigrant Mamadou Berry is murdered, Quinn and Velazquez seek to find his killer; the yearlong investigation pits the detectives against the International Robbin Crew, a ruthless and deadly Atlanta gang.

After a homeless man is shot and killed, Quinn and Velazquez assume it's a simple case; after reports come back matching the murder scene to other ongoing murder cases, the detectives realize they're on the trail of a serial killer.